High Quality Content by WIKIPEDIA articles! The Marsileaceae are a small family of heterosporous aquatic and semi-aquatic ferns, though at first sight they do not physically resemble other ferns. The group is commonly known as the "pepperwort family" or as the "water-clover family" because the leaves of the genus Marsilea superficially resemble the leaves of a four-leaf clover (a flowering plant). Leaves of this fern have sometimes been used to substitute for clover leaves on Saint Patrick`s Day. In all, the family contains 3 genera and 50 to 80 species with most of those belonging to Marsilea.